Change background color of single page – Vertex Theme

Hello! I’ve searched everywhere and can’t solve this problem.

I’m trying to change the background image on just one page. The page number is 635, and this is the page: https://www.ayogalab.com/yoga-corporate/

So far the `body.page-id-635 .fullwidth #main-area {
background: url(‘https://www.ayogalab.com/wp-content/uploads/2014/12/bg.jpg’)
}just fill the content area, and thebody.page-id-635 {
background: url(‘https://www.ayogalab.com/wp-content/uploads/2014/12/bg.jpg’);
}` just changed the background of the footer.

I know that #content-area is the place to change it, but I just want to apply the chance on the 635. Any ideas, please?